/*
** Copyright (C) 2010 Calin Radoni
**
** This file is part of CHScanner.
**
** CHScanner is free software: you can redistribute it and/or modify
** it under the terms of the GNU General Public License as published by
** the Free Software Foundation, either version 3 of the License, or
** (at your option) any later version.
**
** CHScanner is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
** GNU General Public License for more details.
**
** You should have received a copy of the GNU General Public License
** along with CHScanner. If not, see <http://www.gnu.org/licenses/>.
**
** For original copyright see the mt19937.h file !
*/
#include "StdAfx.h"
#include "mt19937.h"

//---------------------------------------------------------------------------

#define M              (397)                 // a period parameter
#define K              (0x9908B0DFU)         // a magic constant
#define hiBit(u)       ((u) & 0x80000000U)   // mask all but highest   bit of u
#define loBit(u)       ((u) & 0x00000001U)   // mask all but lowest    bit of u
#define loBits(u)      ((u) & 0x7FFFFFFFU)   // mask     the highest   bit of u
#define mixBits(u, v)  (hiBit(u)|loBits(v))  // move hi bit of u to hi bit of v

//---------------------------------------------------------------------------

MT19937::MT19937(void)
{
	left = -1;

	idxW = 0;
	idxB = 0;
}

MT19937::~MT19937(void)
{
}

//---------------------------------------------------------------------------

void MT19937::SeedMT(unsigned long seed)
{
    //
    // We initialize state[0..(N-1)] via the generator
    //
    //   x_new = (69069 * x_old) mod 2^32
    //
    // from Line 15 of Table 1, p. 106, Sec. 3.3.4 of Knuth's
    // _The Art of Computer Programming_, Volume 2, 3rd ed.
    //
    // Notes (SJC): I do not know what the initial state requirements
    // of the Mersenne Twister are, but it seems this seeding generator
    // could be better.  It achieves the maximum period for its modulus
    // (2^30) iff x_initial is odd (p. 20-21, Sec. 3.2.1.2, Knuth); if
    // x_initial can be even, you have sequences like 0, 0, 0, ...;
    // 2^31, 2^31, 2^31, ...; 2^30, 2^30, 2^30, ...; 2^29, 2^29 + 2^31,
    // 2^29, 2^29 + 2^31, ..., etc. so I force seed to be odd below.
    //
	// Even if x_initial is odd, if x_initial is 1 mod 4 then
    //
    //   the          lowest bit of x is always 1,
    //   the  next-to-lowest bit of x is always 0,
    //   the 2nd-from-lowest bit of x alternates      ... 0 1 0 1 0 1 0 1 ... ,
	//   the 3rd-from-lowest bit of x 4-cycles        ... 0 1 1 0 0 1 1 0 ... ,
    //   the 4th-from-lowest bit of x has the 8-cycle ... 0 0 0 1 1 1 1 0 ... ,
    //    ...
    //
    // and if x_initial is 3 mod 4 then
    //
    //   the          lowest bit of x is always 1,
    //   the  next-to-lowest bit of x is always 1,
    //   the 2nd-from-lowest bit of x alternates      ... 0 1 0 1 0 1 0 1 ... ,
    //   the 3rd-from-lowest bit of x 4-cycles        ... 0 0 1 1 0 0 1 1 ... ,
    //   the 4th-from-lowest bit of x has the 8-cycle ... 0 0 1 1 1 1 0 0 ... ,
    //    ...
    //
    // The generator's potency (min. s>=0 with (69069-1)^s = 0 mod 2^32) is
    // 16, which seems to be alright by p. 25, Sec. 3.2.1.3 of Knuth.  It
    // also does well in the dimension 2..5 spectral tests, but it could be
    // better in dimension 6 (Line 15, Table 1, p. 106, Sec. 3.3.4, Knuth).
    //
    // Note that the random number user does not see the values generated
    // here directly since reloadMT() will always munge them first, so maybe
    // none of all of this matters.  In fact, the seed values made here could
    // even be extra-special desirable if the Mersenne Twister theory says
    // so-- that's why the only change I made is to restrict to odd seeds.
    //

	register unsigned long x;
	register unsigned long * s;
	register int j;

	x = (seed | 1U) & 0xFFFFFFFFU;
	s = state;
	for(left=0, *s++=x, j=MT19937_N; --j;
        *s++ = (x*=69069U) & 0xFFFFFFFFU);
}

//---------------------------------------------------------------------------

unsigned long MT19937::ReloadMT(void)
{
register unsigned long *p0=state, *p2=state+2, *pM=state+M, s0, s1;
register int    j;

	if(left < -1)
		SeedMT(4357U);

	left = MT19937_N-1, next=state+1;

	for(s0 = state[0], s1 = state[1], j = MT19937_N - M + 1; --j; s0 = s1, s1 = *p2++)
		*p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);

	for(pM = state, j = M; --j; s0 = s1, s1 = *p2++)
		*p0++ = *pM++ ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);

	s1=state[0], *p0 = *pM ^ (mixBits(s0, s1) >> 1) ^ (loBit(s1) ? K : 0U);
	s1 ^= (s1 >> 11);
	s1 ^= (s1 <<  7) & 0x9D2C5680U;
	s1 ^= (s1 << 15) & 0xEFC60000U;
	return(s1 ^ (s1 >> 18));
}

//---------------------------------------------------------------------------

unsigned long MT19937::RandomMT(void)
{
unsigned long y;

	if(--left < 0)
		return(ReloadMT());

	y  = *next++;
	y ^= (y >> 11);
	y ^= (y <<  7) & 0x9D2C5680U;
	y ^= (y << 15) & 0xEFC60000U;
	return(y ^ (y >> 18));
}

//---------------------------------------------------------------------------

DWORD MT19937::GetDWordValue(void)
{
	return RandomMT();
}

WORD  MT19937::GetWordValue(void)
{
	if(idxW==0){
		valW.val = RandomMT();
		idxW = 1;
		return valW.valW.w1;
	}

	idxW = 0;
	return valW.valW.w2;
}

BYTE  MT19937::GetByteValue(void)
{
	switch(idxB){
		case 1 :
			idxB = 2;
			return valB.valB.b2;

		case 2 :
			idxB = 3;
			return valB.valB.b3;

		case 3 :
			idxB = 0;
			return valB.valB.b4;

		default :
			valB.val = RandomMT();
			idxB = 1;
			return valB.valB.b1;
	}
}

//---------------------------------------------------------------------------

/*
int main(void)
 {
	int j;

	// you can seed with any uint32, but the best are odds in 0..(2^32 - 1)

	seedMT(4357U);

	// print the first 2,002 random numbers seven to a line as an example

	for(j=0; j<2002; j++)
		printf(" %10lu%s", (unsigned long) randomMT(), (j%7)==6 ? "\n" : "");

	return(EXIT_SUCCESS);
 }
*/

//---------------------------------------------------------------------------
